Three clones for structural genes coding for proteins secreted from the rat ventral prostate have been identified by hybrid arrest translation. The three cloned inserts have been mapped with restriction endonucleases, and the homologous mRNAs have been shown to be induced by androgens. Human and rat ventral secretory proteins were compared by two-dimensional gel electrophoresis of human and rat prostate secretions. A major low-molecular weight protein is synthesized by both rat and human prostates and has similar but different molecular weight/isoelectric point coordinates (13,000/5.6 rat, 17,000/6.0 human). Homology of these proteins at the cDNA level were investigated. Several tumor lines from human prostate were investigated for the content of RNA sequences homologous to a battery of oncogene probes. There appear to be no human prostate RNA sequences having homology with the 5 oncogene probes utilized in this study.